1. Field of the Invention
This invention describes a new apparatus and method for measuring the angle of torsion on loaded rotating shafts. When the angle is known, it is possible to calculate the torque and the power as the RPM also will be known or measured.
2. Description of the Related Art
The most used method for measuring the power on rotating shafts used in various types of machinery has until now been done by the use of strain gauges glued to the shaft. The signals measured by the strain gauges have been transferred to the instrument electronics and the display by means of sliprings or telemetri. When telemetri is used, it is necessary to have a transmitter mounted on the rotating shaft and powered by a rotating battery, or in newer systems, wireless transfer of power to the strain gauge electronics on the shaft.
A later system uses so-called magnetic hall effect sensors. The sensors pick up signals by means of two gear wheels which are placed on the shaft in an adequate distance from each other. When the shaft is loaded there will be a time delay between the pulses detected by the two hall effect sensors, each of which is sensing on a gear wheel. The time delay between the pulses determine the torsional angle of the loaded shaft. A similar system to this is described in the publication "Antriebstechnik" 33 (1994) No. 8 page 53: "Entwicklung eines robusten beruhrongslosen Drehzahl-Drehmoment-Messystems."
U.S. Pat. No. 4,520,681 is a system which uses a pulse train principle with rotating coders in an adequate internal distance from each other and mounted to the shaft. The torsional angle is measured by means of the time delay between electronic pulses. Two sensors are mounted in an adequate distance from each other, one sensor at each rotating coder. The same time delay between the pulses from the said sensors is measured in electronic counting circuits. In U.S. Pat. No. 4,520,681 either optical or magnetic sensors are used. This system uses similar or identical principles to the system as described at page 53 in the publication "Antriebstechnik" 33 (1994) No. 8.
The above-mentioned systems have the common principle of operation that they will have to use two electronic sensors to make it possible to detect the torsional angle of a loaded shaft.